Placemark visibility

[Mr_Pouille_Sr]

Hello All,

I created a big KML file with thousands of placemarks spread all over the world.
I would like GE4 to display them only when the eye altitude is below 30 miles . (to avoid seeing all these icons everywhere)

How do I define this in KML ? Do I use the region tag ? How ?

Thanks for your help.

[simon_a]

Hello,

Yes, I think this is possible to do now with KML 2.1. There is a good tutorial on regions that should help. I say should because the example shows a couple of polygons - not placemarks - and I've not played with this yet. However, I can't see it not supporting placemarks as well (if you excuse my double-negative!)

http://earth.google.com/kml/kml_21tutorial.html#workingregions

At some stage I want to look at this myself so that I can vary the detail on the London Underground paths I posted a while back as you zoom in. It looks like a very good feature.

Simon

[Mr_Pouille_Sr]

Thanks Simon.
I have spent some time on the Region tag.
I was able to have a point appear only when you zoom close enough.

Here is the code I wrote :

Code:

---

<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://earth.google.com/kml/2.1">
<Document>
<Placemark>
<name>A little boat</name>
<Region>
<LatLonAltBox>
<north>47</north><south>46</south><east>6.9</east><west>5.9</west>
</LatLonAltBox>
<Lod>
<minLodPixels>512</minLodPixels>
<maxLodPixels>-1</maxLodPixels>
</Lod></Region>
<Point><coordinates>6.448056,46.468694,1252</coordinates></Point>
</Placemark>
</Document>
</kml>
 

---

[weatherman22]

Is this something which can be achieved through the "Edit Placemark" function within GE or only by manually editing the kml file? Also, I don't suppose Google Maps uses the data to avoid it just refusing to display more than its set number of placemarks - a heirarchial plotting priority could in theory bypass this limit.

[simon_a]

Hello,

No, you have to edit or generate the KML to do this.

Re Google Maps: Do you mean when it tells you the KMZ file is too large? I wouldn't have thought you'd get round it in this way but you never know. Give it a try!

Simon.

[remosito]

Quote:

---

---

Yes, the region feature is allowing to do exactly that. And while it makes perfect sense and is really quite powerful for overalays and other area related features of google earth. For placemarks I find it quite cumbersome and subideal.

A placemark is a point, the whole idea of area and having to define one plus min and max visible area sizes in pixels doesn't really work out very conveniently when trying to write/define them.

While playing with it all for a lil project here is what I thought would be the most convenient way to handle visibilty for placemarks.

define a maxViewDistance and a minViewDistance for visibility. Plus link it all to styles. So that one can predefine a few different visibility styles that make placemarks visible at different zoom levels then just use those by refering to them inside the placemark. Much, much simpler and straightforward to do from a kml creator point of view. And if there is a region associated with a folder or network link then placemark that do not have a visibility distance associated with them that are contained by the network link or folder they will inherit the folders/network link feature.


As a placemark is always just a point independent of zoom level, there should be no area association within the kml to that notion. It should even be very easy for GE to internally calculate/transfrom it into areas around the placemark and min/max pixel stuff.

I thought I just post my thoughts/feedback. I am sure there will be a kml 2.2 or 3.0 sooner or later and something like that would be extremely handy in my opinion.

[weatherman22]

I don't particularly mind the clutter in GE, I just zoom in, but I wish I could just simply export my kml to Google Maps and it would intelligently show the appropriate density of placemarks at each zoom level to avoid breaching the 65 placemark limit in the view. What it does is just show the first 65, and doesn't attempt to fill in the gaps if you zoom to a smaller area.

This is because my work does not allow GE!